11,618 research outputs found
Chemistry
published or submitted for publicatio
An interactive multi-block grid generation system
A grid generation procedure combining interactive and batch grid generation programs was put together to generate multi-block grids for complex aircraft configurations. The interactive section provides the tools for 3D geometry manipulation, surface grid extraction, boundary domain construction for 3D volume grid generation, and block-block relationships and boundary conditions for flow solvers. The procedure improves the flexibility and quality of grid generation to meet the design/analysis requirements
Review: Do the Different Sensory Areas within the Cat Anterior Ectosylvian Sulcal Cortex Collectively Represent a Network Multisensory Hub?
Current theory supports that the numerous functional areas of the cerebral cortex are organized and function as a network. Using connectional databases and computational approaches, the cerebral network has been demonstrated to exhibit a hierarchical structure composed of areas, clusters and, ultimately, hubs. Hubs are highly connected, higher-order regions that also facilitate communication between different sensory modalities. One region computationally identified network hub is the visual area of the Anterior Ectosylvian Sulcal cortex (AESc) of the cat. The Anterior Ectosylvian Visual area (AEV) is but one component of the AESc that also includes the auditory (Field of the Anterior Ectosylvian Sulcus - FAES) and somatosensory (Fourth somatosensory representation - SIV). To better understand the nature of cortical network hubs, the present report reviews the biological features of the AESc. Within the AESc, each area has extensive external cortical connections as well as among one another. Each of these core representations is separated by a transition zone characterized by bimodal neurons that share sensory properties of both adjoining core areas. Finally, core and transition zones are underlain by a continuous sheet of layer 5 neurons that project to common output structures. Altogether, these shared properties suggest that the collective AESc region represents a multiple sensory/multisensory cortical network hub. Ultimately, such an interconnected, composite structure adds complexity and biological detail to the understanding of cortical network hubs and their function in cortical processing
Constraining Gravitino Dark Matter with the Cosmic Microwave Background
We consider super-gravity models in which the lightest supersymmetric
particle (LSP) is a stable gravitino. The next-to-lightest supersymmetric
particle (NLSP) freezes out with its thermal relic density and then decays
after sec, injecting high-energy photons into the cosmic
plasma. These photons heat up the electron plasma which then thermalizes with
the cosmic microwave background (CMB) via Compton scattering, bremsstrahlung
and double-Compton scattering. Contrary to previous studies which assume
instantaneous energy injection, we solve the full kinetic equation for the
photon number density with a source term describing the decay of the NLSP. This
source term is based on the requirement that the injected energy be almost
instantaneously redistributed by Compton scattering, hence leading to a
time-dependent chemical potential. We investigate the case of a stau NLSP and
determine the constraints on the gravitino and stau masses from observations of
the CMB spectrum by assuming that all gravitino LSPs come from stau NLSP
decays. Unlike the analytical approximations, we find that there may be a stau
mass below which the constraint from the CMB spectrum vanishes.Comment: 8 pages, 6 figures, revtex4, replaced to match published versio
The role and therapeutic targeting of α-, β- and γ-secretase in Alzheimer's disease
Alzheimer's disease (AD) is the most common form of dementia in the elderly and its prevalence is set to increase rapidly in coming decades. However, there are as yet no available drugs that can halt or even stabilize disease progression. One of the main pathological features of AD is the presence in the brain of senile plaques mainly composed of aggregated β amyloid (Aβ), a derivative of the longer amyloid precursor protein (APP). The amyloid hypothesis proposes that the accumulation of Aβ within neural tissue is the initial event that triggers the disease. Here we review research efforts that have attempted to inhibit the generation of the Aβ peptide through modulation of the activity of the proteolytic secretases that act on APP and discuss whether this is a viable therapeutic strategy for treating AD.<p></p>
Alzheimer's disease (AD) is the most common form of dementia in the elderly but as yet there are no drugs that can halt the progression of this disease. In a theory called the ‘amyloid hypothesis’, researchers have proposed that the accumulation of a small protein fragment called beta amyloid or Aβ within brain tissue is the event which triggers Alzheimer's disease. Aβ is a derivative of the longer amyloid precursor protein (APP). Here we review research efforts that have attempted to inhibit the generation of Aβ through modulation of proteins called secretases which cut APP into Aβ.
Author edits made on: 20 May 2015
Recommended from our members
Improving River Flood Extent Delineation From Synthetic Aperture Radar Using Airborne Laser Altimetry
Closed-Form Decomposition of One-Loop Massive Amplitudes
We present formulas for the coefficients of 2-, 3-, 4- and 5-point master
integrals for one-loop massive amplitudes. The coefficients are derived from
unitarity cuts in D dimensions. The input parameters can be read off from any
unitarity-cut integrand, as assembled from tree-level expressions, after simple
algebraic manipulations. The formulas presented here are suitable for
analytical as well as numerical evaluation. Their validity is confirmed in two
known cases of helicity amplitudes contributing to gg -> gg and gg -> gH, where
the masses of the Higgs and the fermion circulating in the loop are kept as
free parameters.Comment: 37 page
- …